D38999 Mil Spec Connector Guide

D38999 Mil Spec Connectors Explained

Part Number Breakdown

D38999 Part Number Breakdown.

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Assembly Instructions

D38999 assembly instruction.

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Part Number Index

List of MIL_DTL-D38999 part numbers.

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Previously known as MIL-C-38999, MIL-DTL-38999 connectors come in four series: Series I, Series II, Series III and Series IV. They are environmentally resistant connectors that use removable crimp contacts and have an operating range of -65 to +200°C.

Series I connectors are bayonet coupled and have high-vibration properties. They are scoop proof and are ideal for heavy wind and moisture environments. They are utilised when a fast disconnect coupling system is required.

Series II connectors are bayonet coupled, are non-scoop proof, and have a low profile, so are used when weight or space is limited, or in low-vibration, high moisture, and strong wind situations.

Series III connectors are coupled by a quick screw Tri start thread, are scoop proof, and are best suited for normal mating and unmating applications and can be used in high temperature, moisture, wind, or vibration environments when used with the correct accessories. Series III connectors are most commonly use in Military and Aerospace designs.

Series IV connectors are coupled by a Breech-Lok mechanism, are scoop proof, lightweight and suitable for blind mating applications, and they also have high-vibration attributes. They are well suited in high wind and moisture environments when used with the appropriate accessories.

38999CouplingScoop ProofDurabilityHigh Impact SchockBend MomentPrice
Series IStandard BayonetYes500Yes650 lbs in$
Series IILow-Profile BayonetNo250No150 lbs in$
Series IIITriple Start ThrededYes500Yes1000 lbs in$$
Series IVBreach-LokYes500Yes - Heavy1000 lbs in$$$

MIL-DTL-38999 Specifications and Datasheets

The most recent MIL-DTL-38999 specification can be downloaded from Defense Logistics Agency Land and Maritime website: click here to download.

Major manufactures of D38999 connectors include Amphenol, TE Connectivity, Glenair, Souriau, Conesys, ITT Cannon and Eaton. You can download each manufacturer's datasheets using links in the following table.

Series ISeries IISeries IIISeries IV
TE Deutsch

Part Number Breakdown

D38999 Part Number Decoder Tool

Try our Part Number Decoder Tool! Enter any D38999 part number in the box below and we will decode it for you. We already entered the "D38999/" prefix so you don't have to.


D38999 connector part numbers are composed of six sections in addition to the D38999 prefix:

The meaning of the codes in each section is explained below.

Shell Type

Series III Series IV Shell Type Description
D38999/20 D38999/40 Receptacle, Wall Mount Flange
D38999/21 D38999/41 Receptacle, Box Mount, Hermetic
- D38999/42 Receptacle, Box Mount
D38999/23 D38999/43 Receptacle, Jam Nut Mount, Hermetic
D38999/24 D38999/44 Receptacle, Jam Nut Mount
D38999/25 D38999/45 Receptacle, Solder Mount, Hermetic
D38999/26 D38999/46 Plug, EMI Grounding Fingers
- D38999/47 Plug
D38999/27 D38999/48 Receptacle, Weld Mount, Hermetic

Shell types 26, 46 and 47 are plugs. All other shells are receptacles. Odd numbered receptacle shell types denote hermetic construction: 21, 23, 25, 27, 41, 43 and 45.

D38999 Shell Styles

Examples of different D38999 shell styles

Material and Finish

Code Image Material Finish
F Aluminum Electroless Nickel Plated (48-hr. Salt Spray)
G Aluminum Space-Grade Electroless Nickel (48-hr. Salt Spray)
H Hermetic Space Grade
J Composite Olive Drab Cadmium (2000-hr. Salt Spray)
K Stainless Steel Corrosion-Resistant Stainless Steel - Firewall (500-hr. Salt Spray)
L Stainless Steel Electrodeposited Nickel (48-hr. Salt Spray)
M Composite Electroless Nickel Plated (2000-hr. Salt Spray)
N Hermetic Stainless Steel, Nickel Plated
S Stainless Steel Nickel Plated (500-hr. Salt Spray)
T Aluminum Nickel PTFE (500-hr. Salt Spray)
W Aluminum Olive Drab Cadmium (500-hr. Salt Spray)
Y Hermetic Stainless Steel, Passivated
Z Aluminum Black Zinc Nickel (500-hr. Salt Spray)
D38999 Finish Materials

Examples of D38999 finish materials

Shell Size

D38999 connectors are available in 9 shell sizes.

D38999 Shell Sizes

D38999 connector shell sizes: A, B, C, D, E, F, G, H ,J

Insert Arrangement

MIL-STD-1560 Insert Arrangements

Click on the insert arrangement to enlarge it. To find the layout of an inseret, look for the insert arrangement code under the shell size letter.

Connector Pin Counts

Shell Size and Insert ArrangementsNumber of Pins
D38999 Series IIIService Rating22D201612
Shell Size and Insert ArrangementsNumber of Pins
D38999 Series IV22D20161210
B5 5   
B98 6   
B99 7   
C4  4  
C98 10   
D5  5  
D18 18   
D35 ???     
D97 84  
E6   6 
E8  8  
E26 26   
F11  11  
G41 41   
H21  21  
H55 55   
J4 488  
J11 2  9
J19   19 
J24  1212 
J29  29  
J43 2320  
J61 61   
F32 32   
G11   11 
G16  16  
A35: 6 #22D, M A98: 3 #20, I B2: 2 #16, I B4: 4 #20, I B5: 5 #20, I B35: 13 #22D, M B98: 6 #20, I B99: 7 #20, I C4: 4 #16, I C8: 8 #20, I C35: 22 #22D, M C98: 10 #20, I D5: 5 #16, II D15: 1 #16 & 14 #20, I D18: 18 #20, I D19: 19 #20, I D35: 37 #22D,M D97: 4 #16 & 8#20, I E6: 6 #12, I E8: 8 #16, II E26: 26 #20, I E35: 55 #22D, M E99: 2 #16 & 21#20, I F11: 11 #16, II F28: 2 #16 & 26 #20, I F30: 1 #16 & 29 #20, I F32: 32 #20, I F35: 66 #22D, M G11: 11 #12, I G16: 16 #16, II G35: 79 #22D, M G39: 2 #16 & 37 #20, I G41: 41 #20, I G75: 4 #8 Twinax, Twinax H21: 21 #16, II H32: 32 #20, I H35: 100 #22D, M H53: 53 #20, I H55: 55 #20, I J4: 8 #16 & 48 #20, I J8: 8 #8 Twinax, Twinax J11: 9 #10 & 2 #20, N J19: 19 #12, I J20: 10 #20 & 13 #16 & 4 #12 & 3 #8 Twinax, N/Coax/Twinax J24: 12 #12 & 12 #16, I J29: 29 #16, I J35: 128 #22D, M J43: 20 #16 & 23 #20, I J46: 40 #20 & 4 #16 & 2 #8 Coax, I/Coax J61: 61 #20, I J90: 40 #20 & 4 #16 & 2 #8 Twinax, I/Twinax

Contact Type

Sealed Connectors

ALess Pin
H1500-Cycle Pin
BLess Socket
J1500-Cycle Socket

Hermetic Connectors

CPC Tail Pin
DPC Tail Socket
XEyelet Pin
YEyelet Socket
Contacts used in D38999 connectors

M39029 Contacts are used in D38999 connectors.

Contact Color Codes

Keying Position

There are six distinct keying positions available for each shell size in the D38999 series of connectors: N, A, B, C, D and E. The keying position is indicated by the last letter in the part number. A plug will only mate with a receptacle with the same keying code. The following figure shows different keying positions for D38999/26FJ61P plug.

Having 6 different keying positions allows use of up to six D38999/26FJ61P plugs in the same space without the possibility of mating a plug with incorrect receptacle.

D38999/26FJ61P Keying Positions

All available keying positions for D38999/26FJ61P

Assembly Instructions


Wire Stripping

  1. Strip wire to required length. When using hot wire stripping, do not wipe melted insulation material on wire strands; with mechanical strippers do not cut or nick strands.
  2. Twist strands together to form a firm bundle.
  3. Insert stripped wire into contact applying slight pressure until wire insulation butts against wire well. Check inspection hole to see that wire strands are visible. If there are strayed wire strands, entire wire end should be re-twisted. When wire is stripped and properly installed into contact, the next step is to crimp the wire inside the contact by using the proper crimping tool.

Contact Crimping

  1. Insert stripped wire into contact crimp pot. Wire must be visible through inspection hole.
  2. Using correct crimp tool and locator, cycle the tool once to be sure the indentors are open, insert contact and wire into locator. Squeeze tool handles firmly and completely to insure a proper crimp. The tool will not release unless the crimp indentors in the tool head have been fully actuated.
  3. Release crimped contact and wire from tool. Be certain the wire is visible through inspection hole in contact.

Contact Insertion

  1. First remove hardware from the plug and receptacle and slide the hardware over wires in proper sequence.
  2. Use proper plastic or metal insertion tool for corresponding contact. Slide correct tool (with plastic tool use colored end) over wire insulation and slide forward until tool bottoms against rear contact shoulder.
  3. Next align the tool and contact up to the properly identified cavity at rear of connector plug. Use firm, even pressure; do not use excessive pressure. It is recommended to start at the center cavity. Contact must be aligned with grommet hole and not inserted at an angle. Push forward until contact is felt to snap into position within insert.
  4. Remove tool and pull back lightly on wire, making sure contact stays properly seated and isn’t dragged back with the tool. Repeat operation with remainder of contacts to be inserted, beginning with the center cavity and working outward in alternating rows.
  5. After all contacts are inserted, fill any empty cavities with wire sealing plugs. (Refer to sealing plug charts for Series III on page 29, for Series I & II and SJT see page 30-31.
  6. Reassemble plug or receptacle hardware - slide forward and tighten using connector pliers. Connector holding tools are recom- mended while tightening back accessories. When using strain relief, center wires at bar clamp. Slide clamp grommet into position and tighten clamp bar screws. When tightening screws, pressure should be applied in the same direction that clamp is threaded to rear threads of connector. When not using clamp grommet, build up wire bundle with vinyl tape so clamp bar will maintain pressure on wires.

Contact Extraction

  1. Remove hardware from plug or receptacle and slide hardware back along wire bundle.
  2. Use proper plastic or metal removal tool for corresponding contact. Slide correct size tool over wire insulation.
  3. Insert plastic or metal removal tool into con- tact cavity until tool tips enter rear grommet and come to a positive stop. Hold tool tip firmly against positive stop on contact shoulder. Grip wire and simultaneously remove tool and contact. (On occasion, it may be necessary to remove tool, rotate 90° and reinsert.)

Part Number Index